There are a number of lens cleaning devices that are described in the prior art that are used on endoscopes, resectoscope, fiberscope catheterization devices and the like that provide for means for cleansing the lens. For example U.S. Pat. No. 4,770,163 granted to Ono et al on Sep. 13, 1988 and U.S. Pat. No. 4,576,146 granted to Kawazoe et al on Mar. 18, 1986 disclose an apparatus for viewing blood vessels and the like by continuously flowing saline fluid through a passage formed in the endoscope at a flow rate that approximates the blood flow rate. Of particular interest is the lens cleaning means disclosed in these patents which show a pair of passageways that include outlets that flow the saline solution in front of the lens. The outlets serve to orient the flow so that the flow discharging from the outlets of each of these passageways oppose each other and hence, according to this patent, the interaction of the opposing fluids keeps the lens clean.
Also of interest as disclosed in the U.S. Pat. No. 4,576,146, supra, is the spiral passageway for injecting the saline solution with a spiral flow to displace the opaque liquid in the region of observation.
U.S. Pat. No. 4,690,140 granted to Mecca on Sep. 1, 1987 discloses an endoscopic tube with a passageway to route clear liquid to circulate around the endoscopic tube. Again this is another attempt to keep the lens clean.
U.S. Pat. No. 4,633,855 granted to Baba on Jan. 6, 1987 also discloses an endoscope that includes a tube mounted internally within the endoscope where the end at the distal end is bent approximately 90 degrees and directed toward the lens so as to blow air or water adjacent the observation window in order to keep it clean.
While these lens cleaning means may be satisfactory in certain biological procedures, they are not satisfactory for others. In the application of video-surgery in laporoscopic and arthroscopic procedures, for example, we have found that creating a film of cleaning fluid to form over the lens surface is a far more satisfactory method of keeping the lens clean or defogged, if it fogs up. In certain instances. injection of the fluid, which may be either water or carbon dioxide, intermittently as needed has proven to be a satisfactory method of keeping the lens clean and defogged.
This invention employs a radial cavity with either partial or full circumferential flow directed over the surface of the lens or lens cover. In other embodiments this invention contemplates incorporating a vortex generator circumferentially mounted around the lens. This invention also contemplates incorporating a judiciously mounted fluid conveying passage integrated within the sheath surrounding the flexible types of medical instruments.